Method for repairing a phase shift mask and a focused ion beam apparatus for carrying out method

ABSTRACT

A method is provided for repairing a phase shift mask. The phase shift mask has a substrate and a shifter containing a defect and disposed on the substrate. An ion beam is irradiated onto the defect while a region of the shifter that includes the defect is supplied with a first gas containing silicon, an oxidizing second gas, and a third gas for controlling an amount of ions from the ion beam which penetrate the region of the shifter to form a silicon thin film on the defect and thereby repair the phase shift mask.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national state application of copendingInternational Application Ser. No. PCT/JP00/02555, filed Apr. 19, 2000claiming a priority date of Apr. 21, 1999, and published in anon-English language.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method for correcting or repairingthe occurrence of defects in a phase shift mask employed inphase-shifting techniques and to a focused ion beam apparatusappropriate for carrying out this method.

Phase shift techniques improve the resolving power of photographicexposure techniques without subjecting the exposure apparatus andresists to any particular changes. Phase shift techniques require aso-called phase shift mask. However, results for phase shift techniquescannot be obtained when defects occur in this shifter. Correctionmethods are therefore preferred for cases where defects occur in theshifter.

One type of shifter defect is when shifter material for part of a regionfor shift forming is defective. In the case of this kind of defect, itis necessary to correct the defect (specifically, to fill it in) usingan appropriate correction material that satisfies conditions such astransparency with respect to the exposing light. The following relatedtechnology is provided as one method of implementing this.

Namely, a shifter defect is irradiated with an ion beam in a gasatmosphere including silicon and oxygen so that a silicon oxide film isbuilt up on the defect and the defect is corrected.Tetraethylorthosilicate (TEOS) is widely used as this gas. TEOS is amaterial that is easy to use from an industrial point of view due toforming a gas easily and having superior step difference coatability forfilms formed, etc.

However, in the case of the aforementioned related correction method,ion beams irradiate shifter defects with only a silicon familyfilm-forming gas being introduced into the processing chamber in thecase of the aforementioned related correction methods. There aretherefore many cases where carbon included in the gas or carbon presentwithin the treatment room is taken in to the film deposited on theshifter defect. Shifter defects are therefore corrected (filled in)using a silicon oxide film with a high carbon content.

It is well known that light transmittance is lower for silicon oxidefilms that are high in carbon content. The aforementioned related methodis therefore not preferable because the light transmittance for exposinglight for the correction part of the shifter falls compared to otherportions of the shifter.

As this invention sets out to resolve these kinds of problems, it is afirst object of this invention to provide a phase shift mask correctingmethod capable of depositing a thin film with a higher lighttransmittance of exposing light than that of the related art as acorrection thin film at shifter defects of the phase shift mask, withthe thin film also having a transmittance that is more appropriate as atransmittance required of a shifter.

Further, it is a second object of this invention to provide a convergingion beam apparatus that can easily implement the correction method ofthe invention.

SUMMARY OF THE INVENTION

In order to achieve the first embodiment, according to the phase shiftmask of this invention, there is provided a method for correcting aphase shift mask, including a step of: irradiating an ion beam onto adefect of a phase shift mask having the defect at a shifter in a mixedgas atmosphere of a first gas for silicon family thin film forming and asecond gas having oxidizability so as to deposit a silicon family thinfilm on the defect. In the method of correcting a phase shift mask ofthe invention, a silicon family thin film is formed on a shifter defectmainly using the first gas. Shifter defects can therefore be correctedusing this silicon family thin film. Namely, defective portions of theshifter can be filled in. Further, with the method for correct ing aphase shift mask of this invention, the second gas, which hasoxidizability, is used together with the first gas. This means thatcarbon included in the first gas and carbon present in the treatmentroom for carrying out mask correction can be changed to carbon dioxide,etc. due to incurring the action of this second gas. Naturally, carbondioxide, etc., generated in this manner is evacuated to outside of thetreatment room by an evacuation apparatus which is normally connected tothe treatment room and which is for evacuating the treatment room forcarrying out mask correction. Therefore, according to the method forcorrecting a phase shift mask of this invention, a silicon family thinfilm with a carbon content that is much smaller compared to the casewhere just the first gas is used as the thin film forming gas is usedcan be deposited on the shifter defect.

It is also preferable for the amount of second gas supplied to be suchthat an amount of oxygen capable of preventing or reducing an extent towhich carbon is contained in the silicon family thin film is included inthe mixed gas atmosphere. This amount may be an amount of oxygen that isdecided upon either by experimentation or theoretically so as to becontained in a mixed gas atmosphere in such a manner that thetransmittance of the silicon family thin film deposited as thecorrection thin film is a kind of transmittance demanded of a shifter.In order to increase transmittance, it is preferable for there to belittle carbon contained in the thin film and preferable for there to beno carbon in the thin film. Therefore, when it is necessary for thetransmittance to be higher, it is one criteria for the second gas to besupplied in such a manner that an amount of oxygen in excess of anamount of oxygen stochiometrically required for forming the siliconfamily thin film is included within the mixed gas atmosphere of thefirst and second gas.

Further, with each embodiment of the method for correcting the phaseshift mask of this invention, the ion beam is a beam of an appropriateion type. Further, it is preferable if an ion beam where the ion type isgallium is used. Gallium has the benefit of a low melting point and thatdesign of the ion source is straightforward, etc.

Further, with the method for correcting a phase shift mask of each ofthe embodiments, it is preferable for a third gas for reducing an extentto which ions derived from the ion beam impregnate the phase shift maskto be supplied together with the first and second gases.

Further, it is also preferable for one type of gas or two or more typesof gas to be selected from halogen gas, hydrogen halide gas and for agas of a substance including a halogen to be used as the third gas. Thereason for this is as follows.

For example, it is well known that a phenomena occurs where gallium istaken in to within this glass substrate when a glass substrate is etchedusing an FIB apparatus employing gallium as an ion source. Making adeduction from this fact, when a thin film is deposited on a defectportion of the shifter using an ion beam, any types of the ions makingup the ion beam may be taken in by the thin film. The transmittance of athin film is then lowered when ions are taken in by the thin film.Therefore, in the preferred examples of the invention, by using a thirdgas together with the first and second gases, ions not required fordepositing the thin film can be changed to compounds through a reactionwith a halogen. For example, gallium ions are changed to compounds suchas GaX2 (where X is a halogen molecule) etc. This compound is evacuatedto outside of the treatment room by an evacuation apparatus which isnormally connected to the treatment room and which is for evacuating thetreatment room for carrying out mask correction. The fear of unnecessaryions being taken into the silicon family thin film can therefore bereduced.

A mixed gas of one type of gas or two or more types of gas selectedfrom, for example, chlorine gas, iodine gas or bromine gas may also beused as the halogen gas for the third gas. A halogen gas subjected tohydrogenation may be provided as the hydrogen halide gas in the exampleshown above. Iodine gas or hydrided iodine gas may also be used. This isbecause the extent of damage to the glass (blanks for phase shiftblanks) is minimal when iodine is included. The transmittance and phasefluctuation of the blanks therefore does not occur.

It is preferable for the amount of third gas supplied to be the minimumamount necessary to prevent or reduce the extent to which ions of theion beam are contained in the thin film deposited on the defect of theshifter. However, when the extent of the vacuum within the treatmentroom deteriorates (for example, when it becomes worse than 5×10⁻⁵ Torr),the ion beam itself can no longer propagate. The amount of third gassupplied can therefore be decided taking into consideration the extentof the vacuum of the treatment room for the whole of the first to thirdgases. Specifically, this is decided either by experimentation ortheoretically.

Further, in order to achieve the second object of this invention, an FIBapparatus of this invention comprises a treatment room capable offorming a vacuum atmosphere, capable of enabling the propagation of anion beam, and capable of housing a phase shift mask having a shifterwith a defect; an ion beam supplying unit for emitting the ion beam; anevacuation unit for evacuating the treatment room; a gas supplying unitfor supplying at least a silicon family thin film forming first gas anda second gas having oxidizability to within the treatment room; acontrol unit for controlling the treatment room, ion beam supply unit,evacuation unit and gas supply unit in such a manner as to at leastexecute processing to deposit a silicon family thin film on the defectby irradiating the defect of the shifter with the ion beam with thefirst and second gases introduced to within the treatment room afterevacuating the treatment room.

According to the FIB apparatus of this invention, a method of correctinga phase shift mask of this application can be implemented in astraightforward manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating an FIB apparatus of an embodiment.

FIG. 2 is a view illustrating a first embodiment of a phase shift maskcorrection method.

FIG. 3 is a view illustrating a second embodiment of a phase shift maskcorrection method.

FIG. 4 is a view illustrating a third embodiment of a phase shift maskcorrection method.

FIG. 5 is a view illustrating a fourth embodiment of a phase shift maskcorrection method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a description, with reference to the drawings, ofembodiments of a phase shift mask correction method and FIB apparatusaccording to the present invention. Each structural component is shownin an abbreviated manner in each of the drawings used in the followingdescription to an extent that enables this invention to be understood.The same structural components in each drawing are given the samenumerals in order to omit duplicity from this description.

FIG. 1 is a outline structural view of the apparatus for illustrating afocused ion beam (FIB) apparatus 10 suited to the embodiments of thephase shift mask correction method of this invention.

This FIB apparatus 10 is provided with a treatment room 11, ion beamsupply unit 13, evacuation unit 15, gas supplying unit 17, sample stage19, secondary charged particle detector 21, image forming device 23 andcontrol unit 25.

A situation is shown in FIG. 1 where a sample 27, i.e. a phase shiftmask 27 having a shifter defect, is placed on the sample stage 19.

The treatment room 11 is a room capable of internally forming a vacuumatmosphere, propagating an ion beam 29, and of allowing the sample 27 tobe inputted and removed. The treatment room 11 for this embodiment has afirst chamber 11 a for housing the sample stage 19, etc., and a secondchamber 11 b cylindrical in shape, for housing the ion beam supply unit13 etc.

The ion beam supply unit 13 supplies the ion beam 29 to the sample 27with the desired beam diameter. The ion beam 29 can irradiate the sample27 at arbitrary positions and the ion beam 29 can scan arbitrary regionsof the sample 27. In order to achieve this, the ion beam supply unit 13of the example structure is provided with an ion source 13 a, a lead outelectrode 13 b, a blanking electrode 13 c, a scanning electrode 13 d andan object lens 13 e, which are positioned within the second chamber 11 bin this order, as is well known.

The ion source 13 a generates ions for irradiating the sample 27. Thision source 13 a is provided in the vicinity of the top part of thesecond chamber 11 b of the treatment room 11. This ion source 13 a maybe an ion source generating one type of ions or an ion source generatingtwo types of ions or more, with one arbitrary type of ion then beingselected for extraction. Gallium, gold, silicon or tin ions may beprovided as ions most appropriate for correcting defects in phase shiftmask shifters. Of these, gallium ions are the easiest for designing anion source for reasons such as the melting point of the gallium itselfbeing low. Silicon ions are also desirable. The reason for this is thatone of the major applications for FIB devices is semiconductor devices.This is because it is very difficult for silicon ions to becomeimpurities for semiconductor substrates and for silicon substrates inparticular.

The lead out electrode 13 b is for leading out ions generated by the ionsource 13 a towards the side of the sample 27.

The blanking electrode 13 c is an electrode used when haltingirradiation of the ion beam 29 to the sample 27. Specifically, the ionbeam 29 going towards the sample 27 can also go in a direction differentto the direction towards the sample 27 and as a result, the irradiationof the ion beam 29 towards the sample 27 is stopped.

The scanning electrode 13 d causes the ion beam 29 to scan the sample27. The object lens 13 e focuses the ion beam 29.

Further, the evacuation unit 15 is for putting the treatment room 11into the desired vacuum state and is constructed from an arbitraryappropriate vacuum pump. With the example structure shown in FIG. 1,this evacuation unit 15 is connected to the first chamber 11 a.

The gas supplying unit 17 includes first gas supply means 17 a andsecond gas supply means 17 b. The gas supplying unit 17 includes a gasgun 17 c for blowing first and second gases into a prescribed limitedregion (for example, a region limited to that including the shifterdefects). In the example structure in FIG. 1, the gas gun 17 c isprovided in the first chamber 11 a and is located facing the sample 27.An example is shown for the example structure in FIG. 1 where there is asingle gas gun but the invention is by no means limited to this example.For example, a gas gun may be provided for each of first to third gassupply means. Further, the gas supplying unit 17 should preferably adopta structure (described in detail later) including a third gas supplyingmeans 17 d for supplying halogen gas as a third gas. In the examplestructure shown in FIG. 1, the gas supplying unit 17 adopts a structureincluding third gas supply means 17 d.

The first gas supply means 17 a supplies gas for forming silicon familythin films. The first gas is sent to the gas gun 17 c via a valve 18 a.Principally, a silicon family thin film is deposited on the defect ofthe phase shift mask shifter by the first gas. A detailed example of thefirst gas is described in the following.

The second gas supply means 17 b supplies a second gas havingoxidizability. After passing through a valve 18 b, the second gas ismixed once with the first gas and then sent to the gas gun 17 c. Thesecond gas is employed to prevent or reduce the extent to whichundesirable atoms are included with the film deposited at the shifterdefect portion. Specifically, the inclusion of carbon in the depositedfilm is prevented or reduced by oxidizing carbon included in the firstgas to produce carbon dioxide etc., and evacuating this to outside ofthe treatment room 11 using the evacuation unit 15. A detailed exampleof the second gas and control of the supply amount is described in thefollowing.

The reason for using the third gas supply means 17 d is to prevent ionsconstituting the ion beam from being included within the film depositedon the defective portions of the shifter. Specifically, the inclusion ofions in the deposited film is prevented by changing the ions intohalides and evacuating the halides to outside of the treatment room 11using the evacuation unit 15. After passing through a valve 18 c, thethird gas is mixed with the first and second gases and then sent to thegas gun 17 c.

The bodies of the first to third gas supply means 17 a to 17 d adoptarbitrary structures appropriate for the type of gas being used. Namely,the gas source for the gas being used is also gaseous. Gas supply meanstherefore adopt structures provided with as gas cylinder 17 b 1 that isfilled up with gas, a control valve 17 b 2 for controlling the amount offlow, a vacuum gauge 177 b 3, and a buffer 17 b 4, etc., as shown, forexample, for the second gas supply means 17 b in FIG. 1. Further, it isalso possible to provide the gas supply means with means (not shown) forheating the gas source or means for controlling the amount of flow etc.,when the gas source for the gas used is a liquid or solid that requiresheating. The sample stage 19 is a stage on which the sample 27 ismounted and which can move the sample 27 to arbitrary positions in threedirections of x, y and z. The z direction is a direction along a linelinking the ion source 13 a and the sample stage 19 and the x and ydirections are directions in a plane perpendicular to this z directionand orthogonal to the z direction, respectively. The xy plane is theplane on which the sample 27 is mounted.

The secondary charged particle detector 21 receives secondary electronsor secondary ions outputted from the sample 27 when the sample 27 isirradiated with an ion beam 29 and converts this intensity to a currentfor outputting to image forming apparatus 23 (for example, a ScanningIon Microscope (SIM)). The secondary charged particle detector 21 isprovided within the first chamber 11 a at a position most suited toreceiving secondary charged particles. The image forming apparatus 23forms an image in response to the secondary charged particle dischargeperformance at each point of the sample 27 that is irradiated with theion beam and this image is displayed at the display unit 23 a. The FIBapparatus 10 can therefore be utilized as a SIM. This function can beutilized, for example, in the case of monitoring corrected portions forafter correction of the shifter defects.

The structures of the secondary charged particle detector 21 and theimage forming apparatus 23 themselves are well known and a detaileddescription thereof is therefore omitted here.

The control unit 25 controls the treatment room 11, ion beam supplyingunit 13, evacuation unit 15, sample stage 19, secondary charged particledetector 21 and image forming apparatus 23 so as to operate inprescribed manners. The control unit 25 can, for example, be constructedusing apparatus including a computer, a sensor provided at anappropriate position, and an electronic circuit. In particular, thecontrol unit 25 in this case controls the treatment room 11, ion beamsupplying unit 13, evacuation unit 15 and gas supplying unit 17 in sucha manner that, after the inside of the treatment room 11 is evacuated toa prescribed vacuum, at least processing to deposit a silicon familythin film on the defective portion is implemented by irradiating thedefective portion of the shifter of the phase shift mask 27 with the ionbeam 29 with the first and second gases introduced to within thetreatment room 11. This kind of control is investigated, for example,experimentally in advance to get appropriate ranges for, for example, adegree of vacuum, ion beam intensity, and flow quantities for the firstto third gases, etc. The control unit then monitors these parameters ona vacuum gauge and flowmeter, etc., and control is then exerted so thatoperations obey a predecided order.

Next, a description is given of embodiments for several phase shift maskcorrection or repair methods of this invention. Several situations whereshifter defects are corrected using the FIB apparatus 10 describedreferring to FIG. 1 are now described. This description is set forthwith reference to FIG. 2 to FIG. 4.

FIG. 2 is a view illustrating a first embodiment of a correction method.At a phase shift mask 27A where a shifter 27 b is provided separately ona substrate 27 a for phase shift mask use, an example is shown ofcorrecting the phase shift mask 27A where a defect (defective portion)27 c occurs at part of the shifter 27 b. The views are side views (thesame also applies for FIG. 3 to FIG. 5 in the following) payingattention to displaying the vicinity of the sample stage 27 and gas gun17 c of the FIB apparatus 10.

First, the phase shift mask 27A is placed on the sample stage 19.Evacuation then takes place via the evacuation unit 15 so as to bringabout a prescribed degree of vacuum within the treatment room 11. Theinvention is not limited in this respect, but evacuation to give a highvacuum state of within 10⁻⁵ Torr is preferable.

Next, the first and second gases are supplied (blown) from the gassupplying unit 17 to a region including the defect 27 c via the gas gun17 c. At this time, the amount of second gas supplied is an amount ofoxygen capable of preventing or reducing the extent to which carbon iscontained within the silicon family thin film deposited on the defect 27c of the shifter 27 c. An amount is therefore supplied in such a mannerthat an amount of oxygen capable of making the transmittance of the thinfilm the transmittance that is demanded of shifters is included withinthe treatment room 11.

This kind of amount can be realized by the control unit 25 controllingthe flow ratio of the first and second gases. Further, this kind of flowratio can be decided in advance either experimentally or theoreticallyand a flow amount controller for the first and second gas supply means17 a and 17 b can be controlled by the control unit 25 based on the flowratio.

For example, when tetraethylorthosilicate (TEOS) gas is used as thefirst gas, and oxygen is used as the second gas, then if the TEOS flowamount is taken to be 1, then an oxygen flow amount of 0.001 or more ispreferable (this is 10 or more in cases where stoichiometry is to befulfilled).

It is preferable for the flow amount to be a flow amount within thisrange that is capable of realizing the transmittance demanded of ashifter. This is, of course, only one example.

A gas including both or one of oxygen atoms and nitrogen atoms, togetherwith silicon atoms can be used as the first gas. Further, a gas (silane,etc.) that positively does not include oxygen atoms and nitrogen atomsbut includes silicon atoms may also be used. However, the former gas,i.e. a gas including both or one of oxygen atoms and nitrogen atoms,together with silicon atoms, is preferred as the first gas. This takesinto consideration ease of forming a silicon family thin film using theFIB apparatus.

When a gas including silicon atoms and oxygen atoms is used as the firstgas, an oxidized silicon family thin film can be deposited on defectiveportions of the shifter. Further, when a gas including silicon atoms andnitrogen atoms is used as the first gas, a nitrided silicon family thinfilm can be deposited on defective portions of the shifter. Stillfurther, when a gas including silicon atoms, oxygen atoms and nitrogenatoms is used as the first gas, an oxided/nitrided silicon family thinfilm can be deposited on defective portions of the shifter.

One type of gas or a mixed gas of two or more types of gases selectedfrom the gas compound shown in equation (1) in the following can beproduced as a gas containing silicon atoms and oxygen atoms.(R—O)₄Si  (1).

Specifically, one type of gas or two or more types of gas selected from,for example, tetraethylorthosilicate (TEOS) gas, tetramethyorthosilicate(TMOS) gas, and tetrapolopolysilane (TPOS), can be used. TEOS is themost preferred of these gases. This is because TEOS is a material thatis easy to use from an industrial point of view due to forming a gaseasily and having superior step difference coatability for films formed,etc.

Further, one type of gas or a mixed gas of two or more types of gasesselected from oxygen, ozone, water vapor and NO_(x) (where x shows thecombination ratio of the nitrogen and oxygen) can be used as the secondgas. It is also possible to select one type of gas or two or more typesof gas from oxygen, ozone and water vapor as the second gas. Thesesecond gases are easy to procure and manage, and are also preferablewith regards to eliminating carbon. Oxygen or water vapor are still morepreferable as the second gas.

A prescribed region including the defect 27 c is scanned by the ion beam29 (FIG. 2(A)) with the first and second gases supplied in the abovemanner. The result of this scanning is that a silicon family thin film27 d is formed on the defect 27 c (FIG. 2(B)). The thin film 27 d is ofa thickness required to shift the transmitted light by the requiredphase angle. This film thickness can be managed using, for example, theion beam scanning frequency, etc. The relationship between the ion beamscanning frequency and the film thickness of the thin film is thereforeobtained in advance by experimentation. This data is then stored inmemory (not shown) of the control unit 25 and the film thickness can becontrolled based on this data. A phase shift mask 27B with the shiftdefect 27 c corrected can therefore be obtained using the above seriesof processes.

By varying the flow amount of the second gas with respect to the firstgas it is possible to change the refractive index of the silicon familythin film 27 d. It can then be considered possible to adjust the phaseor exposing light to a certain extent at the silicon family thin film 27d using this flow ratio.

FIG. 3 is a view illustrating a second embodiment of a correctionmethod. The thickness of a portion of the substrate 27 a of the phaseshift mask is made thin. At this portion itself, at the phase shift mask27C constituted by the shifter 27 e, an example is shown where the phaseshift mask 27C with a defect (defective portion) 27 f occurring at partof the shifter 27 e is corrected.

Correction processing of the phase shift mask 27C is realized (FIG.3(A)) using the same procedure as described with reference to FIG. 2. Asilicon family thin film 27 g can then be deposited in the defect 27 fusing this correction processing (FIG. 3(B)). A phase shift mask 27Dwith the defect 27 f corrected can also be obtained in this manner.

FIG. 4 is a view illustrating a third embodiment of a correction method.At a phase shift mask 27E where a shifter 27 a is provided separately ona substrate 27 a for phase shift mask use, an example is shown ofcorrecting a phase shift mask 27E where the film thickness t1 of theshifter 27 h is insufficient by an amount t from the film thicknessrequired of the shifter. The film thickness required of the shifter is afilm thickness for providing a prescribed phase difference (typically, aphase difference of 180 degrees) between the light passing through theshifter 27 h and the light passing through the original lighttransmittance portion.

Correction processing of the phase shift mask 27E is realized (FIG.4(A)) using the same procedure as described with reference to FIG. 2. Asa result of the correction processing, a thin film of a silicon familythin film 27 i corresponding to the film thickness t of the insufficientportion is deposited on the shifter 27 h (FIG. 4(B)). As a result, aphase shift mask 27F with the defect corrected, i.e. with theinsufficient film thickness corrected, is obtained.

In each of the correction processes described with reference to FIG. 2to FIG. 4, a second gas is used together with the first gas. Carbonincluded in the first gas, etc. is therefore oxidized by the second gasbefore being evacuated to outside of the treatment room 11 by theevacuation unit 15. The silicon family thin film deposited on theshifter defect in any of the cases therefore has a lower carbon contentthan compared with the case where just a first gas is used as a gas. Theshifter defect is therefore corrected to a thin film with a hightransmittance of exposing light.

Halogen gas may also be supplied as the third gas together with thefirst and second gas during implementation of the phase shift maskcorrection method of this invention. As a result, redundant ions of theions constituting the ion beam 29 that do not contribute to depositionof the thin film therefore react with halogens and are put into gaseousform. The redundant ions are then evacuated to outside of the treatmentroom 11 by the evacuation unit 15. Ions constituting the ion be am aretherefore prevented from being included in the thin film deposited onthe shifter defect and improvement of the transmittance of the thin filmis achieved. It can be considered that these results are obtainedregardless of the type of ions used.

When the third gas is used, the amount of third gas supplied isdifferent depending on the ion beam dose and the acceleration speed, andit is preferable for this amount to be obtained through experiment, etc.It is preferable to decide the amount of third gas supplied in such amanner that the vacuum within the treatment room 11 that depends on thefirst gas, second gas and third gas can be maintained to such an extentthat the operation of the ion beam is not hindered (this is by no meanslimiting, but to an extent that a high vacuum in excess of 5×10⁻⁵ Torris maintained).

It is also preferable to do the following when implementing the phaseshift mask correction method of this invention. A description is givenwith regards to this with reference to FIG. 5.

There are also many cases where an edge portion P of a thin film 271deposited using gas and an ion beam at a defect (defective portion) 27 kof the shifter 271 sags (FIG. 5(A)). Problems such as not being able toshift the exposing light to the desired phase angle and the shape of theedge pattern being detrimentally influenced occur when sagging occurs.The unnecessary portion P of this thin film 271 is then removed (byetching) using an ion beam 29 so as to match the contour of the shifter27 j. Correction to a shifter having an appropriate shape can then beachieved by this deletion (FIG. 5(B)).

This etching can be implemented using a function that the FIB apparatus10 is given to begin with. Further, monitoring of whether or not theedge portion sags or monitoring of the portion being etched when etchingof the sagging edge portion can be carried out by an image formingdevice that the FIB apparatus 10 possesses to begin with.

Processing of unnecessary portions may also be carried out using a laserbeam in place of the ion beam 29. Processing using this laser beam maybe carried out by a laser beam emitting device provided within thetreatment room 11 or by a separately prepared laser beam emittingdevice.

A description is given in the above of an embodiment of this inventionbut this invention is by no means limited to the aforementionedembodiments and various modifications and alterations are possible.

For example, the arrangement of each structural component of the FIBapparatus is by no means limited to the example in FIG. 1. Further, thestructure of each of the parts 11, 13 and 17 is by no means limited tothe above example.

Further the applied example of the correction method is by no meanslimited to the above example and may also be applied to various types ofphase shift masks.

INDUSTRIAL APPLICABILITY

As is dear from the above description, according to the method forcorrecting a phase shift mask of this invention, there is provided amethod for correcting a phase shift mask, including a step of:irradiating an ion beam onto a defect of a phase shift mask having thedefect at a shifter in a mixed gas atmosphere of a first gas for siliconfamily thin film forming and a second gas having oxidizability so as todeposit a silicon family thin film on the defect. Carbon which it isfeared will be contained in the silicon family thin film is thereforeoxidized and evacuated to outside in a gaseous form. The likelihood ofcarbon being contained in the thin film deposited on the defect portionof the shifter is therefore prevented or reduced. Shifter defects cantherefore be corrected using thin films with a higher transmittance thanthose of the related art.

Further, according to the fib apparatus of this application, there isprovided a prescribed treatment room, ion supplying unit, evacuationunit, gas supplying unit and control unit, and the method for correctinga phase shift mask of the present invention can therefore be implementedeasily.

1. A method for repairing a phase shift mask, comprising the steps of:providing a phase shift mask having a substrate and a shifter disposedon the substrate; and irradiating an ion beam onto a defect of theshifter while supplying to a region of the shifter that includes thedefect a first gas containing silicon, an oxidizing second gas, and athird gas for controlling an amount of ions from the ion beam whichpenetrate the region of the shifter to thereby form a silicon thin filmon the defect and repair the phase shift mask.
 2. A method according toclaim 1; wherein the supplying step includes the step of supplying thesecond gas to provide an amount of oxygen for preventing the formationof carbon in the silicon thin film or reducing an extent to which carbonis contained in the silicon thin film.
 3. A method according to claim 1;wherein the supplying step includes the step of supplying the second gasto provide an amount of oxygen so that a transmittance of the siliconthin film is the same as a transmittance of the shifter.
 4. A methodaccording to claim 1; wherein the supplying step includes the step ofsupplying the second gas to provide an amount of oxygen capable ofpreventing the formation of carbon in the silicon thin film or reducingan extent to which carbon is contained in the silicon thin film and sothat a transmittance of the silicon thin film is the same as atransmittance of the shifter.
 5. A method according to claim 1; whereinthe supplying step includes the step of supplying the second gas toprovide an amount of oxygen in excess of an amount of oxygenstoichiometrically required for forming the silicon thin film.
 6. Amethod according to claim 1; wherein the first gas comprises a singletype of gas or a mixture of two or more types of gases selected from agas compound represented by the formula (R—O₄)—Si, where R represents analkyl group.
 7. A method according to claim 1; wherein the second gascomprises one or more types of gases selected from the group consistingof oxygen, ozone and water vapor.
 8. A method according to claim 1;wherein the first gas comprises tetraethylorthosilicate (TEOS) and thesecond gas comprises a gas selected from the group consisting of oxygen,ozone and water vapor.
 9. A method according to claim 1; wherein theions of the ion beam comprise gallium ions.
 10. A method according toclaim 1; wherein the third gas comprises a gas selected from the groupconsisting of halogen gas, hydrogen gas, hydrogen halide gas and a gasof a substance including a halogen.
 11. A method according to claim 1;further comprising the step of removing unnecessary portions of thesilicon thin film using an ion beam or a laser beam in order to obtainalignment of the silicon thin film with an outline of the shifter.
 12. Amethod according to claim 1; wherein the defect of the shifter comprisesone of a defect in a portion of the shifter and a deficiency in athickness of the shifter.
 13. A focused ion beam apparatus comprising: atreatment room for housing a phase shift mask having a shifter with adefect; an ion beam supply unit for emitting an ion beam and directingthe ion beam in the treatment room toward the phase shift mask; anevacuation unit for evacuating the treatment room to provide therein avacuum atmosphere; a gas supply unit for supplying a first gascontaining silicon, an oxidizing second gas, and a third gas into thetreatment room; and a control unit for controlling the evacuation unitto evacuate the treatment room and for controlling the ion beam supplyunit to irradiate the ion beam onto the defect of the shifter whilecontrolling the gas supply unit to supply the first gas, the oxidizingsecond gas, and the third gas to a region of the shifter including thedefect to form a silicon thin film on the defect and thereby repair thephase shift mask, the third gas being selected for reducing an amount ofions from the ion beam which penetrate the region of the shifter.
 14. Afocused ion beam apparatus according to claim 13; wherein the controlunit controls the gas supply unit to supply the second gas to provide anamount of oxygen for preventing the formation of carbon in the siliconthin film or reducing an extent to which carbon is contained in thesilicon thin film.
 15. A focused ion beam apparatus according to claim13; wherein the control unit controls the gas supply unit to supply thesecond gas to provide an amount of oxygen so that a transmittance of thesilicon thin film is the same as a transmittance of the shifter.
 16. Afocused ion beam apparatus according to claim 13; wherein the controlunit controls the gas supply unit to supply the second gas to provide anamount of oxygen for preventing the formation of carbon in the siliconthin film is that same as or reducing an extent to which carbon iscontained in the silicon thin film and so that a transmittance of thesilicon thin film is the same as a transmittance of the shifter.
 17. Afocused ion beam apparatus according to claim 13; wherein the controlunit controls the gas supply unit to supply the second gas to provide anamount of oxygen in excess of an amount of oxygen stoichiometricallyrequired for forming the silicon thin film.
 18. A focused ion beamapparatus according to claim 13; wherein the ions of the ion beamcomprises gallium ions.
 19. A method for repairing a phase shift mask,comprising the steps of: providing a phase shift mask having a defectportion containing a defect; disposing the phase shift mask in anatmosphere of a gas mixture comprised of a first gas containing silicon,an oxidizing second gas, and a third gas; and irradiating an ion beamonto the defect portion of the phase shift mask to form a silicon thinfilm on the defect while the third gas controls an amount of ions fromthe ion beam which penetrates into the defect portion of the phase shiftmask to thereby repair the phase shift mask.
 20. A method according toclaim 19; wherein the phase shift mask comprises a substrate and ashifter disposed on the substrate; and wherein the defect of the phaseshift mask comprises a missing portion of the shifter.
 21. A methodaccording to claim 19; wherein the phase shift mask comprises asubstrate and a shifter disposed on the substrate; and wherein thedefect of the phase shift mask comprises an insufficient thickness ofthe shifter.
 22. A method according to claim 19; wherein the second gasprovides an amount of oxygen for preventing the formation of carbon inthe silicon thin film or reducing an extent to which carbon is containedin the silicon thin film.
 23. A method according to claim 19; whereinthe second gas provides an amount of oxygen so that a transmittance ofthe silicon thin film is the same as a transmittance of the shifter. 24.A method according to claim 19; wherein the second gas provides anamount of oxygen capable of preventing the formation of carbon in thesilicon thin film or reducing an extent to which carbon is contained inthe silicon thin film and so that a transmittance of the silicon thinfilm is the same as a transmittance of the shifter.
 25. A methodaccording to claim 19; wherein the second gas provides an amount ofoxygen in excess of an amount of oxygen stoichiometrically required forforming the silicon thin film.
 26. A method according to claim 19;wherein the first gas comprises a single type of gas or a mixture of twoor more types of gases selected from a gas compound represented by theformula (R—O₄)—Si, where R represents an alkyl group.
 27. A methodaccording to claim 19; wherein the second gas comprises one or moretypes of gases selected from the group consisting of oxygen, ozone andwater vapor.
 28. A method according to claim 19; wherein the first gascomprises tetraethylorthosilicate (TEOS) and the second gas comprises agas selected from the group consisting of oxygen, ozone and water vapor.29. A method according to claim 19; wherein the ions of the ion beamcomprise gallium ions.
 30. A method according to claim 19; wherein thethird gas comprises a gas selected from the group consisting of halogengas, hydrogen gas, hydrogen halide gas and a gas of a substanceincluding a halogen.